The present invention relates to an electronic system with the function of backing up data from one or more electronic units installed therein.
An example of conventional methods for backing up information from each electronic unit installed in a system is disclosed in Japanese Unexamined Patent Publication No. H05-155295.
This disclosed method uses a backup RAM provided in a specified ECU (Electrical Control apparatus) in ECUs installed in a system.
This backup RAM is constantly connected to an internal power supply in the system. The backup RAM can thus hold memory contents even after the system power supply is turned off.
In the operation of the system, the specified ECU collects data stored in each ECU at predetermined intervals and then stores the collected data in the backup RAM as backup information.
After the power supply in the electronic system is turned off, and turned on again, the specified ECU reads out the backup information stored in the backup RAM and sends it to each ECU installed in the system.
The disclosed method sends the information stored in each ECU to the specified ECU, and the specified ECU centrally backs up the sent information in the backup RAM. The specified ECU is configured to send the information to each ECU when the system starts up.
If the specified ECU needs to individually send the backup information to at least one of the ECUs when the system is running, such as in a case where at least one of the ECUs is reset, the whole system would need be reset to resend the backup information to every ECU.
When the whole system is not restarted, at least one of the ECUs, which is reset, controls a target device with the default values (previously set values required for the control of the target device).
At least one of the reset ECUs need continue to perform the control process until it learns the values required for the control of the corresponding target while controlling the target device with the default values.
These problems may occur in a system that has a plurality of microcomputers and requires to back up data, which is stored in each of the microcomputers, in a specified microcomputer in the microcomputers.